1. Technical Field
The present disclosure relates to control over a driving system for a vehicle, the driving system including an electric motor that serves as a driving source for propelling a vehicle and an electric oil pump that supplies oil to a cooling and lubrication required portion including the electric motor.
2. Description of Related Art
There is known a driving system for a vehicle. The driving system includes an electric motor that serves as a vehicle driving source and an electric oil pump for supplying oil to a cooling and lubrication required portion including the electric motor. In the thus configured driving system, the electric motor is cooled and a gear mechanism, and the like, are lubricated by operating the electric oil pump in response to a traveling state of a vehicle.
Incidentally, as the electric oil pump operates, noise due to the operating sound of the electric oil pump occurs. As measures for noise, Japanese Patent Application Publication No. 2007-22296 (JP 2007-22296 A) describes that the operating range of an engine is controlled to a low rotation and high torque (a range in which noise is large) in proportion to a vehicle speed. In the low rotation and high torque range of the engine, generally, thermal efficiency is high, while noise is large. In response to this, since running noise increases as the vehicle speed increases, noise of the engine becomes inconspicuous because of the running noise, with the result that noise that is perceived by a driver is reduced. As described in JP 2007-22296 A, it is conceivable to make noise from the electric oil pump inconspicuous by operating the electric oil pump such that noise from the electric oil pump is hidden by running noise that increases in proportion to the vehicle speed.
However, when noise is made inconspicuous by running noise during traveling as described in JP 2007-22296 A, it is difficult to make noise from the electric oil pump inconspicuous in a low vehicle speed range. A lubrication system, and the like, that require operation of the electric oil pump need to be operated even at a low vehicle speed. However, if only running noise of the vehicle is provided as means for making noise that accompanies the operation of the electric oil pump inconspicuous, the operation of the electric oil pump is limited at a low vehicle speed, so the amount of oil that is supplied to the cooling and lubrication required portion can be insufficient. Alternatively, when the electric oil pump is controlled such that the amount of oil that is supplied to the cooling and lubrication required portion is ensured, noise from the electric oil pump is conspicuous in the low vehicle speed range.